1. Field of the Invention
This invention relates to the manufacture of ophthalmic lenses. Specifically this invention relates to a method for manufacturing ophthalmic lenses using pre-blocked lens blanks which includes articulation edging.
2. Background of the Invention
Ophthalmic lens manufacturing typically requires many steps, devices and machines operated by highly trained technicians. For example, lens generation typically involves a skilled technician mounting a lens blank on a block responsive to a desired finished lens prescription in a blocking process. Blocking is the process of rigidly affixing a lens blank to a holding device in a precise orientation in order to perform forceful machining operations on the blocked lens blank. De-blocking is the process of removing a lens blank, generally at least partially processed, from a lens blank. Re-blocking, is a subset of blocking, and is blocking a lens blank that has been previously blocked, such as re-blocking for edging following surfacing operations. Pre-blocking within the meaning of this application is a sub-set of blocking and refers to a blocking procedure that requires that the lens blanks be blocked without prior knowledge of the lens prescription variables and without information about the frame size and shape.
In the art of manufacturing ophthalmic lenses today, blocking for surfacing generally requires substantive lens prescription information, and in order to optimize lens thickness, frame dimension information is also needed. In the art today, blocking for edging requires both lens prescription information and frame dimension information. Significant amounts of time are required for blocking. Each blocking step introduces some error. Manual blocking for surfacing is very complicated and requires a high degree of expertise to perform. Expensive devices are in use to simplify the process. Typical blocking media (chemical compounds used for blocking) are heated to the liquid form, i.e. melted, so that it flows over and conforms to the surfaces of the lenses to be blocked. This heated media must be allowed to cool sufficiently, generally about 12 to 15 minutes, before machining can commence. Without sufficient cooling there is a high risk of auto or self de-blocking resulting in a scrapped lens blank. Further complicating the process is that optical flaws can be created if the blocking media is too hot. The blocking compounds used in the art today are too expensive to dispose of after each use, so complicated, time consuming, and messy reclamation systems are employed for recycling.
Following blocking for surfacing of a lens blank in prior art procedures, the technician then uses one machine that performs surfacing on the lens blank and a second machine for fining and/or polishing with a lap tool. Operation of these machines produces finished uncut lenses, which only require edging to become finished lenses. These then need to be de-blocked and marked-up and re-blocked again for edging on yet another machine. Each of these steps requires expensive skilled operator intervention. Each machine used in the process requires lab space and has associated acquisition and maintenance costs.
Some attempts to address the limitations of the conventional prior art processes have been proposed, for example in what has been called the “Coburn process” there is a teaching of how a lens can be blocked for both surfacing and edging without de-blocking and re-blocking between the surfacing and edging steps, but the “Coburn process” produces skewed edges in the final lens configuration that limits its use.
Further, a company known as Super Systems, Inc. has a system for pseudo-pre-blocking for surfacing Front Surface Multi-focals and Semi-Finished Single Vision lens blanks. This process is referenced as pseudo-pre-blocking as the front surface Multi-focals are blocked with a “pre-determined amount of inset and drop” which places the optical center at a predetermined position relative to the multifocal feature. The pseudo-pre-blocking in this system cannot be economically done due to the pre-determined amount of inset and drop, and thus is not commercially done, for lenses with prism in the lens prescription specification. Hundreds of lens types would each have to be pseudo-pre-blocked with hundreds of different possible prism specifications. Lens thickness can not be systematically optimized when the optical center location is predetermined as it is in this system. This pseudo-pre-blocking system is for surfacing of lenses only. Semi-finished lenses made with this system must still be de-blocked, marked-up, and re-blocked for edging.
Spoilage occurs when lens blanks are surfaced or edged for the wrong eye or for the wrong job and when the selected lens blanks are made of the wrong type of lens material or have the wrong coatings. Therefore there is a need for a system of verifying that the correct species of lens blank is being used when making a lens. Further, there is a need for automatically verifying that the correct species of lens blank is being used for making a lens.
There remains is a need for a method of ophthalmic lens manufacture that may eliminate or reduce the amount of skilled labor required and there is a need for a method of ophthalmic lens manufacture that may reduce the number of machines or devices required to produce ophthalmic lenses.